The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Air is drawn into an engine through an intake manifold. A throttle valve controls airflow into the engine. The air mixes with fuel from one or more fuel injectors to form an air/fuel mixture. The air/fuel mixture is combusted within one or more cylinders of the engine. Combustion of the air/fuel mixture generates torque.
Exhaust resulting from the combustion of the air/fuel mixture is expelled from the cylinders to an exhaust system. The exhaust includes nitrogen oxides (NOx), such as nitrogen oxide (NO) and nitrogen dioxide (NO2), and other exhaust constituents. The exhaust system includes one or more components, such as a selective catalytic reduction (SCR) catalyst and/or a lean NOx trap, that reduce NOx in the exhaust before the exhaust is expelled to atmosphere.